The invention relates to novel immunosuppressive peptides; novel pharmaceutical compositions containing the peptides; and therapeutic uses of the peptides.
Radiotherapy and chemotherapy are well-established treatment methods for malignant disease. Cells, which grow and divide rapidly, are most vulnerable to the effects of radiation and cytotoxic agents. Among those effected are tumor cells, and normal cells including hair and intestinal cells, and cells of the hemopoietic and immune systems. Damage to normal cells of the hemopoietic and immune systems by radiation and cytotoxic agents often has life-threatening consequences, and it limits the ability to administer a full therapeutic dose.
There has been extensive research to identify agents which will protect normal hemopoietic and immunologic cells from the effects of radiotherapy and chemotherapy, or aid in the reconstitution of cells suppressed by these therapies. For example, transforming growth factor beta-1 has been reported to be useful for protecting hematopoietic stem cells from the myelotoxicity of chemotherapeutic drugs or radiation therapy (U.S. Pat. No. 5,278,145 to Keller et al.) A lyophilised composition containing human albumin in thymosin alpha 1 was also reported to exert a preventative activity against progression of leukaemia""s in mice whose immune systems were severely damaged by treatment with cytostatic agents or radiation treatment (89EP 102569 to Lattanzi). Hemopoietic growth factors such as interleukin-3 and CSF have been used to potentiate immune response or assist in reconstituting normal blood following radiation-or-chemotherapy-induced hematopoietic cell suppression (WO8805469 to Anderson et al., U.S. Pat. No. 4,959,455 to Ciarletta et al; U.S. Pat. No. 4,999,291).
Semina et al. (Radiatsionnaya Biologiya Radioekologiya 33(3), 1993; WO 8906134) have shown that the levorotary (L) enantiomer of the dipeptide H-Glu-Trp-OH acts as an immunostimulant and can induce the proliferation of cells. As such, these dipeptides are useful in reconstituting hemopoietic and immune cells after chemotherapy or irradiation therapy.
The inventors have surprisingly found that the dextrorotary (D) enantiomers of the peptides of the present invention have the opposite activity as compared to their L-enantiomeric counterparts.
In particular, the inventors have found that the D enantiomers of the peptides are immunosuppressive and inhibit the proliferation of cells. In contrast, the corresponding L-enantiomers are immunostimulants and induce the proliferation of cells. Consequently, the peptides of the present invention are useful in protecting cells from the damaging effects of irradiation and chemotherapy. Both irradiation and chemotherapy act on rapidly proliferating or dividing cells (i.e cells in S-phase) while the peptides of the present invention inhibit the proliferation of the cells (i.e. cells in G-phase) thereby making the cells resistant to the damaging effects of the radiation or chemotherapy. The protected cells can then be induced to proliferate (or reconstitute) using agents known in the art such as the L-peptides described by the inventor in his co-pending application Ser. No. 08/894,963, Now U.S. Pat. No. 6,051,683 which is incorporated by reference in its entirety. Broadly stated, the present invention relates to a peptide of formula I
X-A-D-Trp-Yxe2x80x83xe2x80x83(I)
wherein X is hydrogen, glycine, alanine, leucine, isoleucine, valine, N-valine, proline, tyrosine, phenylalanine, tryptophan, D-alanine, D-leucine, D-isoleucine, D-valine, D-N-valine, D-proline, D-tyrosine, D-phenylalanine, D-tryptophan, xcex3-aminobutyric acid, or xcex6-aminocaproic acid; A is D-glutamic acid, or D-iso-glutamic acid; D-iGlu and Y is glycine, alanine, leucine, isoleucine, valine, N-valine, proline, tyrosine, phenylalanine, tryptophan, D-alanine, D-leucine, D-isoleucine, D-valine, D-N-valine, D-proline, D-tyrosine, D-phenylalanine, D-tryptophan, xcex3-aminobutyric acid, xcex6-aminocaproic acid, hydroxyl or an amide group.
In a preferred embodiment, the present invention relates to the peptide H-D-iGlu-Trp-OH or H-D-Glu-D-Trp-OH.
The invention also relates to analogues of the peptides of the invention and cyclic peptides. The terms xe2x80x9cpeptidexe2x80x9d and xe2x80x9cpeptidesxe2x80x9d used to herein include these analogues and cyclic peptides.
The invention also contemplates a method for preparing the peptides. The method should result in good yield of the product using simple and efficient steps.
The peptides of the invention have many therapeutic applications. In particular, the peptides of the invention can be used whenever it is desirable to inhibit cell proliferation. Accordingly, in one embodiment, the present invention relates to a method of inhibiting cell proliferation comprising administering an effective amount of a peptide of the invention to a cell or animal in need thereof.
In another embodiment, the present invention relates to a method of ameliorating graft survival comprising administering an effective amount of a peptide of the invention to an animal in need thereof.
In a further embodiment, the present invention relates to a method of protecting cells during hyperthermia comprising administering an effective amount of a peptide of the invention to an animal in need thereof.
The peptides of the invention have been shown to be non-toxic and to protect the cells of the hemopoietic and immune systems when the cells are exposed to radiation or chemotherapeutic agents. Accordingly, in another embodiment, the invention relates to a method of protecting cells of the hematopoietic and immune systems in an animal during radiation or chemotherapy comprising administering an effective amount of a peptide of the invention to an animal in need thereof.
In yet another embodiment, the invention al so relates to a method of immunosuppressing an immune system in an animal comprising administering an effective amount of a peptide of the invention to an animal in need thereof. In one embodiment, the peptide may be administered prior to an organ or bone marrow transplant.
The present invention also includes a pharmaceutical composition comprising one or more peptides of the invention and a pharmaceutically acceptable carrier.
Additional objects, features, and ad vantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description.